Commercial and residential buildings often use fuel fired appliances such as water heaters, furnaces and boilers. In many cases, the fuel fired appliances include a combustion chamber with a flue that is vented to outside of the building (e.g. atmosphere) via a vent pipe or the like. During off-cycle periods, the fuel fired appliances can lose significant heat through the vent pipe or chimney by natural convection and/or conduction. To help reduce these losses, a damper can be installed either at the flue exit or in the vent pipe. Alternatively, two or more dampers may be used, such as a flue damper installed upstream of a draft diverter of the fuel fired appliance, and a vent damper installed downstream of the draft diverter.
In some cases, electric motor controlled flue dampers may be used and controlled by a damper controller or the like. In some cases, the damper(s) may be controlled to open when combustion starts, and close immediately or sometime after combustion stops. This may help minimize the off-cycle heat losses that may occur through the vent pipe or chimney of many fuel fired appliances.